This invention relates to a novel energy-absorption device useful, for example, in the construction of vehicle bumpers or other applications requiring buffering against dynamic impact.
Energy-absorbing crash protection systems have within recent years assumed an important position in the automobile industry, especially because of the development of certain criteria and adoption of certain standards by the U.S. Department of Transportation. While the present goal of the Department of Transportation is to require automobile manufacturers to equip cars with bumpers capable of absorbing collision impact at a speed of up to 5 mph, it can be expected that these requirements will be gradually raised to cover more realistic collision speeds.
The present trend in automobile bumper construction includes the use of more steel, the resulting bumpers being quite heavy and expensive; of hydraulic shock absorbers, which function very well in longitudinal collisions but tend to lose their effectiveness in lateral or angular collisions; of rubber inserts in steel bumpers, which do offer a certain degree of additional protection at an added cost; and of polyurethane foam pads placed between the car body and the steel bumper.
An effective energy-absorbing device should be capable of yielding on impact and recovering, either partially or completely, after the impact. It would thus appear that simply making bumpers of heavier steel and with heavier reinforcements is not the answer because such bumpers cannot effectively yield on impact. An elastomeric bumper would have a much better capability of absorbing the collision energy because of the elastomer's inherent resiliency. Various elastomeric bumpers have been disclosed in the art. Thus, U.S. Pat. No. 3,638,985, for example, describes an arcuate, resiliently deformable bumper, which has web means in the shape of a grid projecting inwardly. Such a bumper, made of a high quality elastomer, is said to be able to absorb a large amount of energy.
French patent 2,089,868 (to Saab-Scania Ab), discloses a modular elastomeric automobile bumper component in the shape of a substantially rectangular hollow block divided into smaller, substantially rectangular compartments by means of portions intersecting at right angles.
A commercially useful elastomeric energy-absorbing device should be made of an elastomer having the right mechanical properties within the expected operating temperature range. The device must satisfy size and weight limitations usually imposed by vehicle or other equipment manufacturers as well as any existing or proposed government performance standards. The question then becomes twofold: how to achieve the desired goal in the most economical manner (using the least amount of elastomer), and how to distribute most effectively a given amount of rubber.